Computational Studies of the Spin Trapping Potential of Gallic Acid and its Derivatives in the Reactions with Hydroxyl Free Radicals

Abstract

Gallic acid (GA) and its derivatives are naturally occurring phenolic antioxidants that have been proposed as spin-trapping agents to study radical reactions in vivo. Despite significant interest, this has not been previously studied using computational chemistry methods. To assess this potential, electronic structure calculations for GA, MG, EG, hydroxyl radical (·OH), and the radical addition spin adducts were calculated using Hartree Fock (HF) and Density Functional Theory (DFT), the B3LYP functional for DFT and the 6-31G(d), cc-pVXZ, and aug-cc-pVXZ (X = D, T) basis sets, followed by extrapolation to the Complete Basis Set limit. Gibbs free energy calculations were also performed to evaluate the spontaneity of the radical adduct formation reaction. The stabilization energy and Gibbs free energy trends were MG > GA > EG. The results demonstrate that while electron-donating substituents can enhance radical adduct stability, geometric distortion from bulky substituents can counteract the effect.